Clamping Force Evaluation of a Bolted Joint According to the Variation of Torque and Angle Applied

Bolted joints are frequently applied in the automotive industry. Although apparent simplicity for this clamping solution, phenomena involved in the tightening procedure of the bolt are complex and very difficult to control in a production line. During the tightening process, portion of the energy is dissipated as friction and portion is consumed in elastic and plastic deformation of the bolted joint. In order to ensure the function of the joint requirements, only the second one is relevant. The problem is that the tightening process control method only monitors the "torque and angle" variables and not directly the deformation of the joint. Therefore, the monitoring is also dependent of the friction's variable, whose influence is very significant. This work aims to evaluate the clamping force behavior of a bolted joint used at small car front suspension subframe, using a transducer built with eight linear strain gauges. Ninety assemblies were controlled and the results were evaluated statistically and discussed here.